The present invention concerns a method and a device for passively aligning at least one optic fibre and at least one component.
The component may be, as will be more clearly seen hereafter, an auxiliary alignment support for optic fibres or an opto-electronic component and, in this latter case, may be a photo-detector or a photo-emitter (for example, a diode or laser type).
In particular, the invention makes it possible to assemble a standard optic fibre tape and an array of emitting or receiving optical circuits.
The invention also concerns the connection of a matrix of optic fibres to a VCSEL matrix, in other words, vertical cavity surface emitting lasers, or a matrix of photo-detectors of this type.
Moreover, the invention relates to opto-electronic components that one wishes to assemble to high capacity optical links (for example, optic cables fitted with connectors) as well as the assembly of xe2x80x9cparallelxe2x80x9d optic fibres and juxtaposed opto-electronic components.
The invention also makes it possible to form direct optical connections between light emitters and other light emitters intended for the optical pumping of the former emitters.
The coupling of an optic fibre and a laser beam emitter requires a precise alignment of this component and the fibre, in general an alignment to an accuracy of around 10 xcexcm, the required precision being even greater in the case of monomode optic fibres. For the coupling of an optic fibre and a detection component (for example a VCSEL used as a photo-detector) the same accuracy is needed as for the coupling between the fibre and the emitter component.
If one considers the example of the coupling of an optic fibre and a laser emitter, a widely used alignment technique is the active alignment of the fibre and this laser emitter, wherein a voltage is applied to this emitter in order to emit a laser beam. When the alignment is obtained, the fibre is fixed to the laser emitter by welding or bonding.
This active alignment technique leads to high costs for the assembly obtained thereof.
For this reason, a passive alignment technique has been sought. In this case, the relative positioning then the fixing of the fibre and the emitting or receiving element are carried out without voltage being applied (for the element) nor luminous flux. The fibre and the element are mechanically wedged against each other and then fixed in a precise manner.
For example, a passive assembly technique for an optical fibre and a laser rod, whose emission is lateral, has been described. This assembly uses a support comprising a V groove, which is provided for the positioning of the optic fibre. This optic fibre is stuck in this V groove and the laser rod is hybrided with precision onto the support, opposite the fibre.
This technique enables an accuracy of around 1 xcexcm to 5 xcexcm to be obtained. It enables an optic fibre and a lateral emission laser to be assembled but it does not enable the assembly of a fibre and a VCSEL type laser, which emits light via one face.
Nevertheless, this technique has been modified in order to allow this type of assembly. In this case, optical or mechanical means are used to place the VCSEL at 90xc2x0 to the optic fibre.
However, this modified passive alignment technique requires the use of complex means, in particular auxiliary alignment means.
In fact, if one wants to assemble an array of VCSEL (emitters or detectors) to optic fibres, the prior art shows that it is necessary to use an auxiliary alignment means and a support for the assembly.
A xe2x80x9cdirectxe2x80x9d assembly of a VCSEL emitting via the rear face and an optic fibre is however described in the following documents:
(1) A. Keating et al., 6 Gbit/s optically pumped 1.55 xcexcm VCSEL operating up to 105 xc2x0 C., Revue Photonics, vol. 12, nxc2x0 2, 2000, pp. 116-118.
(2) Y. Kobayashi et al., Improvement of coupling efficiency for passive alignment of stacked multifiber tapes to a vertical-cavity surface-emitting laser array, Jpn. J. Appl. Phys., vol. 36, Part I, nxc2x0 3B, 1997, pp. 1872-1875.
This known assembly is obtained by forming a guiding hole in the substrate of the VCSEL.
In the invention, as in the prior art, one seeks to resolve the problem of the direct and precise coupling between at least one optic fibre and at least one opto-electronic component (emitter or detector), such as, for example, a xe2x80x9cplanarxe2x80x9d type, this coupling being passive.
In order to be clearer, let us consider the specific problem posed by the direct and precise assembly of a VCSEL and an optic fibre.
Document (1) describes how optic fibres and opto-electronic devices (VCSEL) may be passively aligned by boring guiding holes in the substrate that bears the devices and by sliding the optic fibres into these holes.
This known technique has however the disadvantage of requiring the formation of guiding holes directly in the substrate where the devices are built up.
However, it involves a substrate made out of GaAs and therefore fragile, which risks breaking during the manufacture of the devices if it is drilled beforehand, or which risks breaking during the final manufacturing operations of the assembly if this substrate is bored after the manufacture of the devices.
Moreover, this substrate in GaAs, rendered fragile by the holes, may break during the introduction of the optic fibres.
In addition, the boring of precise dimensions in a material such as GaAs is a little known technique and therefore difficult to implement.
An aim of the present invention is to resolve the aforementioned disadvantages.
The invention proposes forming at least one housing, comprising an alignment guide, directly on a component, in such a way that one is able to align an optic fibre and the component without a support or an auxiliary alignment wedge.
In a specific embodiment of the invention, where one wishes to connect optic fibres to one or several opto-electronic chips, the invention proposes forming alignment guides in the substrate of each chip, after hybriding this chip (or chips) onto the control circuit of this (these) chip(s).
For the formation of the alignment guides and the positioning of the fibres, the chipxe2x80x94control circuit assembly is more resistant than the chips on their own.
More precisely, an aim of the present invention is a method for passively aligning at least one component and at least one optic fibre, wherein the component comprises a substrate that has first and second faces opposite each other, this method being characterised in that:
at least two slots are formed in the substrate, starting from the first face of this substrate, wherein these two slots form a cross and define, at their intersection, a housing that is provided to receive one end of the optic fibre, and
this end is placed in the housing.
According to a first embodiment of the method according to the invention, the component is an opto-electronic component comprising at least one active zone formed on the side of the second face of the substrate, where this active zone is intended to emit or capture light and must be optically coupled to the optic fibre, and the slots are formed in such a way that the housing is positioned opposite the active zone of the opto-electronic component.
This opto-electronic component comprises, for example, at least one vertical cavity surface emitting laser, formed by the active zone.
According to a second specific embodiment, the component is an auxiliary alignment support for optic fibre(s).
According to a specific embodiment of the invention, this auxiliary alignment support is coupled to an opto-electronic component comprising at least one active zone, wherein the housing of the auxiliary alignment support is formed in such a way as to be positioned opposite this active zone when the auxiliary alignment support is coupled to the opto-electronic component.
In this case, the end of the optic fibre may be placed in the housing before, or after, the coupling of the auxiliary alignment support to the opto-electronic component.
In an example of the invention, several copies of the component (in particular when it involves an auxiliary alignment support) are formed, on a same substrate, then slots for each of these copies are formed and these copies are then separated from each other.
According to a specific embodiment of the method according to the invention, in the case where the component is an opto-electronic component, several copies of this opto-electronic component are formed on a same substrate, then slots for each of these copies are formed, then these copies are separated from each other, they are hybrided, on the side of their second faces, to an electronic control circuit and the respective optic fibre ends are placed in the housings formed on the copies, wherein these housings are provided to receive these ends.
However, according to a preferred embodiment, several copies of the opto-electronic component are formed on a same substrate, these copies are separated from each other, they are hybrided, on the side of their second faces, to an electronic control circuit and then slots are formed for all of the copies thus hybrided and the respective optic fibre ends are placed in the housings formed on the copies, wherein these housings are provided to receive these ends.
In the invention, the substrate may be transparent to the light intended to be captured or emitted by the optic fibre or, on the contrary, may be opaque to this light.
In this latter case, a hole, provided to open out the housing into the second face of the substrate, is in addition formed (before or after the slots).
This hole may be formed using a laser.
In the invention, the slots are, for their part, preferably formed using a cutting machine comprising a circular saw.
Another aim of the present invention is a device for passively aligning at least one component and at least one optic fibre, the component comprising a substrate that has first and second opposite faces, wherein this device is characterised in that it comprises at least two slots formed in the substrate leading from the first face of the substrate, wherein these two slots form a cross and define, by their intersection, a housing that is provided to receive one end of the optic fibre.
According to a specific embodiment of the device according to the invention, the component is an opto-electronic component that is hybrided, on the side of the second face of the substrate, to an electronic control circuit.